<!doctype html>

<title>11 Lifecycle Methods - React From Zero</title>

<script src="https://unpkg.com/react@15.4.2/dist/react.js"></script>
<script src="https://unpkg.com/react-dom@15.4.2/dist/react-dom.js"></script>
<script src="https://unpkg.com/babel-core@5.8.38/browser.min.js"></script>

<div id="app"></div>

<script type="text/babel">

// If we use component classes, our components inherit
// a bunch of methods, which get called by React at specific
// times to allow us to get more control over our components
// a few of them we already met in lesson 9
// Here are a few new. Not all of them, but the most important ones

var TRANSLATION_FROM_SOMEWHERE = 'Text from a synchronous source.'

var MyComponent = React.createClass({

  // This method is for default prop values
  // it gets called before the props are given to our component
  // the "real" props override them if there are any
  getDefaultProps: function() {
    return {
      iGetOverriden: 'default',
      iStayAsIAm: 'default',
    }
  },

  // This method is called before a component got mounted to the DOM
  // it returns values that are used for this.state
  getInitialState: function() {
    return {serverData: null}
  },

  // This method gets called right before the component is mounted
  // can be used to initialize some synchronous configuration, that should
  // be available before the component renders
  componentWillMount: function() {
    this.TEXT = TRANSLATION_FROM_SOMEWHERE
  },

  // This method will be called right after the component got mounted
  // it's a good place to start some asynchronous tasks.
  // For example on the first mount it shows a loading message
  // then componentDidMount is called and gets some server data.
  componentDidMount: function() {

    var component = this

    // We clean up the data and get new from somewhere
    function loadData() {

      component.setState({serverData: null})

      getServerData(function(data) {
        component.setState({serverData: data})
      })

    }

    // Initial data load
    loadData()

    // We simulate a server request every 4 seconds
    this.updateInterval = setInterval(loadData, 4000)

  },

  // This method will be called before the component gets removed from the DOM
  // a bit like a destructor. Here we can do some cleanup.
  componentWillUnmount: function() {

    clearInterval(this.updateInterval)

  },

  // This method is called before a render when new props or state is available
  // it won't be called on the first render or if this.forceUpdate() is used
  // it can be used if some state or prop changes don't require a rerender
  shouldComponentUpdate: function(nextProps, nextState) {

    // we want to render on every change, this is the default behaviour
    return true

  },

  render: function() {
    return (
      <h2 style={{width: 400, margin: 'auto'}}>

        Overriden Prop: {this.props.iGetOverriden}<br/><br/>

        Default Prop: {this.props.iStayAsIAm}<br/><br/>

        {this.TEXT}<br/><br/>

        {this.state.serverData
          ? this.state.serverData
          : 'Loading...'
        }
      </h2>
    )
  },

})

function getServerData(fn) {
  setTimeout(function() { fn('Data Loaded!') }, 700)
}

ReactDOM.render(<MyComponent iGetOverriden={'override'}/>, document.getElementById('app'))

</script>